1. Field of the Invention
The present invention relates to an improved photografting process and apparatus for imparting chemically bonded fluorocarbon finishes to textile fibers and textiles made therefrom, in which the fibrous substrate is in contact with a gaseous mixture of fluoroolefins in an inert diluent gas, and subjected to the action of ultraviolet light under predetermined conditions.
2. Brief Description of the Prior Art
It is known in the prior art that unsaturated monomeric materials can be grafted onto polymeric substrates as disclosed in such patents as U.S. Pat. No. 2,956,899 to Cline, U.S. Pat. No. 3,412,175 to Magat, et al., and U.S. Pat. No. 3,933,607 to Needles, et al. The process disclosed in the Cline patent involves irradiation of polymeric substrates in the presence of a controlled amount of oxygen, after which the activated substrate is contacted with a liquid polymerizable monomer. The Magat, et al. patent is concerned with a grafting technique which involves contacting a polymeric substrate with a fluoridated monomer in the presence of high energy radiation. As with the Cline process, the polymeric substrate has to be soaked in the liquid monomer or in a solution thereof. Needles, et al. discloses a vapor phase photografting of monomers onto polymeric substrates, requiring a two-step process in which the substrate is first treated with a wetting agent after which the substrate is contacted with a photosensitizer and with the monomer in the presence of a radiation source.
Another suggested approach has been to use a fluorocompound with a functional group that will be either adsorbed strongly to the surface or undergo a chemical reaction with the fiber surfaces. One example of this type of bonding involves the chromium complex of various acids containing long chain fluorocarbon groups: ##STR1##
If this reaction occurs on the surface of a fiber such as nylon, the chromium will complex with amino groups, thus absorbing the fluorocarbon tail to the fiber surface. Unfortunately, such "complex" linkages will not withstand normal laundering or dry cleaning processes. Textile Res J, 27, 369 (1967); Textile Res J., 28, 233 (1958). It has also been reported that treatment of cotton fabric with perfluoroheptene-1 or perfluorobutadiene in aqueous KOH and NaOH formed fluorocarbon grafts to cellulose. The application of fluorocarbon finishes to wool by plasma polymerization has also been reported. Textile Res J., 42, 307 (1972); Sci.-Chem., A10 (3), 579 (1976).
The textile industry has tried many finishes to improve the surface property of e.g., polyester fibers but its smooth and chemically passive nature makes it extremely difficult to retain any finish on the surface. Some soilrelease schemes have been developed for polyester/cotton blends by an electrical discharge method, but a noticeable stiffening of the "hand" of the material was noted. Textile Res J., 42, 307 (1972).
It is also known in the art to treat aromatic polyamides to impart thereto flame-proofing properties by subjecting aromatic polyamides to fluorocarbon treatment to irreversibly modify the polyamides with fluorocarbon grafts. J. Appl. Polymer Sci., 21, 2538 (1977). The known method is, however, not entirely satisfactory, requiring an undesirably long time to effect effective fluorocarbon grafting.